The invention relates to extensometers.
It is important that the studs or bolts securing steam chest covers or turbine cylinder flanges, for example, are correctly tensioned to avoid either loss of steam if they are under-tensioned or premature failure of the studs or bolts if they are over-tensioned. Ideally, the studs or bolts should be stressed by a predetermined amount of strain when they are tensioned. The stress in the stud or bolt depends on the strain produced by the applied tension. The corresponding extension can be calculated from the stress so that the strain in the stud or bolt can be effectively measured by proper measurement of the extension of the stud or bolt. To date, however, it has not been possible to measure the extension with sufficient accuracy.
It is an object of the invention to provide an extensometer which can be used to measure the extension of a component such as a stud or bolt.